Vault conditioner with control means



A. TRASK VAULT CONDITIONER WITH CONTROL MEANS Dec. 8, 193

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VAULT CONDITIONER WITH CONTROL MEANS Filed Dec. 18, 1950 6 Sheets-Sheet 3 FIE- 3 b k K? j 1 WW imp - i fillezz 77-ask 2% arweys 6 Sheets-Sheet 4 A. TRASK VAULT CONDITIONER WITH CONTROL MEANS Dec. 8, 1953 Filed Dec. 18, 1950 L u p H v M \6 Wm x M6 M6 W 6 6% W6 %k om w W .33 H Lu M. l Wm W N% NM 6mm Dec. 8, 1953 sK 2,661,603

VAULT CQNDITIONER WITH CONTROL MEANS Filed Dec. 18, 1950 6 Sheets-Sheet 5 FIE]- 5 Patented 8, 1953 UNITED STATES TENT OFFICE 2,661,602 VAULT ooNmTtoNEaWIrii contact MEANS This invention relates to unitary machines for automatically controlling the relative hu'rnidity and temperature of merchandise storage vaults, and more particularly to self-contained machine's constructed to meet the storage requirements of furs, foods, seeds and other products sensitive to water vapor and temperature.

There has been a continually expanding need in the handling of merchandise sensitive to excessive humidity and temperature for a humidity and temperature controlling machine completely selfcontained in one cabinet which may be easily installed in a room or vault. A compact, small unit at a comparatively low cost is urgently needed.

Refrigeration machines have been in the past and are now extensively used to condition the storage rooms and vaults for food, furs, etc, but these conventional systems have been individually engineered and installed in separate pieces into the premises of the purchaser. These conventional cold storage installations are costly and are not adapted to automatic humidity control.

An object of this invention is a compact, selfcontained, low cost machine constructed for automatically controlling the temperature and humidity of a storage room.

Another object is a storage conditioning ma chine constructed to cool and recirculate air in a storage room in parallel With the natural thermosyphonic tendency of the air to .fiow in response to heat leakage into the room. 7

A further object is the construction of a storage conditioning machine to withdraw air from the ceiling level of a storage room, cool it and reduce its humidity, and then discharge it at the floor level of the room.

Another object is the embodiment of a fumigant evaporating means in the air recirculating system of the machine for fumigating storage rooms.

Still another object is a storage conditioning machine of the refrigeration type constructed to use its h at of operation for reduction of relative humidity in a storage room. Y

A still further object of this invention is a machine cf type described wherein the temperature ci a refrigerant evaporator is caused to drop in response to an increase of relative humidity in the air of a storage room.

Other purposes, objects and advantages to this invention will be understood from the detailed soeciflcation and explanation following:

This invention lies in a storage conditioning machine embodying a compression type refrigeration system including a compressor, amotor, a

rat'or and an air circillatbl'olvf Whi constructed with ineahs fol reducing the volume or air circulated over the evaporator in response to a rise in relative hui'n'i'dfryer the anibieht air. 7

This iflventioi'l contemplates several variatiofis of structure by which air flow volume over the amt "titer i at be reduced. It may be reduced by reducing the 315883. of at 7211210123 Sliced. motor driving the blower or fan moving air over the evaporator. It may be re'd'u ''d by layassing a portion or the an moved around the evaporator. It be reduced by restricting the air inlet to the evaporator blower or fan. I a

The preferred methcd of reducing the how volume of air over the evaporator contemplated by this invention is shown in the drawings. dbllbl inlet evaporator blower with a centrally partitiohed blower when is used. A shutter calls is constructed to close one inlet to the blot/er and render one half er the timer \lvheel meters we, thereby reducing the air now issues the stepcrator to approximately one half.

This inv'hti'on er'nbr'aces constructions which (new air iroi'n the ceiling level of a room, cool the an", and then discharge the cooled air at the es i- 1'e'v"e1'. Iirlprove'd" distribution or cooled air is gained by virtue the heavier Weight of cooled ail Whlfi causes it to spread in the straturn at the floor level. As the air warms it rises to be replaced with freshly cooled air underneath. The warmest air in the more collects at the ceiling level from whence it is Withdrawn by machines embodying this invention to be again cooled and recirculated.

condenser and an attaining rapid hiii'nidity reduction in response to a demand rgii steredby an electric hiiinidistat. The'reciruiated air is stantiallyin temperature and volume, and a pornon of isthen'ld tlir ugh a separate compressor conipar'tilient of therhachine where the air reheated or the heat or operation of the compress'or and the career-ester motor. The cooling operation condenses Water vapor from the air which in this process becoziies saturated. The reheating operation reduces the relative humidity of the air using the heat generated by the operationof the compressor and its motor which would otherwise serve fio-usfiil purpose. i I

All of the foregoing constitute some of the prin cipal objects and advantages of the present invention, others of which will become apparent from the following" description-and from-the drawings,-

in vv'hich Fig.- 1 is a front elevation View of astorage con This invention eriibraces a novel structure for contact in a reduced sub= ea ditioning machine embodying this invention with the front enclosure panels removed in section to show the interior of the machine,

Fig. 2 shows a horizontal cross section of Fig. 1, through sectional lines 2-2, looking downward upon the compressor compartment;

Fig. 3 shows a vertical cross section of Fig. l with the left side enclosure panel removed to show the interior of the machine, the left cooling coil is also removed to show the blower assembly;

Fig. 4 is a side elevation view of the right hand side of the cabinet enclosing the machine; the air intake duct from the ceiling level being shown and also an auxiliary side air inlet opening;

Fig. 5 is a wiring diagram showing the electrical components of the machine and the circuits of the automatic control system of this invention for controlling both the relative humidity and the temperature of the air in a storage room;

Fig. 6 shows a portion of the cool air duct extending through the compressor compartment of the machine with its dampers and damper controls;

Fig. 7 shows a horizontal cross section through the duct assembly of Fig. 6, looking downward upon section line l-'i;

Fig. 8 shows a vertical side elevation view of the cool air blower assembly in the evaporator compartment Fig. 9 shows a vertical cross sectional view of the cool air blower and its shutter assembly taken on sectional line 99 of Fig. 8; and

Fig. 10 shows a vertical sectional view through a garment storage vault in which a storage conditioning machine embodying this invention is installed, the direction and method of air circulation within the vault being shown with arrows.

Referring to Fig. l, a steel cabinet 1 is shown enclosing the mechanism of the machine. A horizontal partition 2 divides the interior of the cabinet I into an upper chamber 3 and a lower chamber d. In the upper chamber 3 are two refrigerant evaporators 5, an expansion valve 6, a cool air blower i and a blower motor 8. The top cover i-A of the cabinet i is the top of upper chamber 3 in which two air openings l9 provide entrance for recirculated room air. A horizontal partition 9, transverse of cabinet I directs incoming air to the outward faces of the two refrigerant evaporators 5.

A cool air duct Iii shown separately in Figs. 6 and 7 extends from blower 7, through lower chamber A to plenum chamber i I, under partition 12, which divides the lower chamber i from plenum chamber H. A cool air discharge grille i3 with horizontal louvers iii directs the cooled air outward at the floor level parallel with the floor.

In the lower chamber t there is shown a compression type refrigeration condensing unit consisting of a reciprocating compressor l5, an electric motor It for driving the compressor, a conventional water cooled condenser-receiver unit I? and a cooling coil 18 for cooling this compressor compartment with cool water on its Way to the condenser unit ll.

There is a cold water inlet pipe 5E3 entering the cabinet I to provide cooling water for the water.

cooled condensing unit. Water inlet pipe 58 communicates with water control valve 5i, which is a conventional refrigerant pressure controlled valve. Water control valve 5! communicates with cooling coil l8, used for cooling the air in the condensing unit compartment 4. The outlet of coil i8 communicates with the water inlet of the condenser receiver unit i7, through pipe 52. The water outlet of the condenser-receiver unit ll is a pipe 53, terminating outside the cabinet I.

There is an evaporator pan 54 under each evaporator 5 for catching the condensate. These pans have drain outlets through pipes which join and communicate with drain outlet pipe 55.

A shallow horizontal pan 5? covers substantially the bottom of the cabinet l and provides a bottom to plenum chamber H. A conduit 58 extends from the outside of the cabinet 5 to communicate with pan St for filling it with liquid iumigant.

Referring to Figs. 8 and 9, blower '5 comprises a blower housing LA and a double inlet blower wheel as mounted on shaft 51 by means of hub 62 and solid circular disc 53 to which the blades of the blower wheel are attached. The circular disc to acts as a partition within the blower wheel to divide in substantially equal portions the volume of inlet air taken into double inlet openings 54 at each side of blower housing 'i-A. Thus circular disc E53 is located substantially midway between the two blower air inlet openings fi l. A shutter assembly ii is assembled to the right hand side of blower '5 covering the right hand side blower air inlet opening iii. Blower motor drives blower l by means of pulleys and a V-belt in the conventional manner.

Upon blower housing "i-A is mounted a damper motor 25 connected with operating linkage 26-A to shutter assembly 21 shown in a closed position. Additional linkage ZZ-A extends from shutter 25 to lever 22, which is operably connected with gate in cool air duct It. A link i i-A from lever 22 to lever 2d controls the opening and closing of gate in conjunction with the opening and closing of gate 23 in response to the operation of damper motor 29 through linkages Et-A, Z2-A and F t-A. A spring 26 connected to lever 22 counteracts the pull of damper motor 2:; through said linkages to return the dam er motor arm to its at rest position.

In Figs. 1, 3 and i are shown air inlet ducts 21 attached to openings iii in cabinet I. These ducts extend to the ceiling level of the room in which the machine operates, as shown in Fig. 10. Grille 213, provides an auxiliary air inlet opening from the storage room to the space in front of the evaporator coils ii and provides an inspection opening for viewing the fin surface of the coils during operation of the machine. Grille 28 is provided with a manually operable shutter Eli-A for closing the opening of grille 2B or controlling the amount of auxiliary recirculated air admitted to the evaportors. An inspection door 29 is provided on both sides of the cabinet I to facilitate installation, inspection, adjustment, replacement and repair.

In Fig. 3, there is shown a panel 3% to which may be assembled the electrical control instruments for the machine shown diagrammatically in Fig. 5.

In 5, the wiring diagram of the machine, a 230 volt, 6% cycle, 3 phase line is connected to conductors ill, H and E2 of the machine, which connect with a three pole magnetic motor starting switch which starts and runs compressor motor 55 through conductors i3, '55 and 15.

One phase of the line circuit is used to'actuate the electrical control instruments. Conductor it used as a neutral wire of the single phase control circuit connects with clock motor 32, relay to, relay 35, the actuating magnet of motor starter 38 and also transformer 36.

a ecneoe A manual double pole, double throw switch 31 is connected to energize selectively either one of two circuits. In its right hand position of switch 35 contact is made between conductors ii and 13 to establish a circuit from line conductor 7-2 to conductor '49, energizing blower motor 8. The second pole of blower motor 8 is connected to line conductor ll by conductor Bil to operate the blower motor only.

When manual switch 3-! is set in its left hand position, a contact is made between conductors 8| and S2 to establish a circuit from motor starting switch 38, through conductors i5, 8|, 82 and is, to operate blower motor 3 during the time that motor starting switch 38 is closed to operate compressor motor [6.

When manual switch BI is set in its left hand position, a second contact is established to connect conductor ll with conductor 83 to establish a circuit from line conductor #2 to a pair of contacts on relay to, to switch 85 and clock motor as of defrosting timer 32, which actuates its switch 85. Clock motor at is arranged to open switch 65 for a few minutes out of each three hours that cloci; motor 8% is energized and oper ating. When switch 35 is open, a circuit is established by the normally closed position of relay it from conductor 83 through conductors Si and N to energize and operate blower motor 8. At such time only blower motor 8 in the machine will be operating, and this operation is for the purpose of defrosting coils 5.

When manual switch 3| remains in its left hand position and switch 85 of the defrosting timer is closed, then relay til is energized and contact is made between conductor 83 and conductor 38 to energize conductor 88 to pressure switch 3;. The pressure switch 33 is normally closed. It is arranged to be opened only when the refrigerant pressures in the refrigeration system of the machine exceed or become depressed below the normal operating pressures of the system.

While pressure switch 33 is normally closed, contact is made between conductor 88 and conductor 39 to energize conductor 39, which in turn energizes humidistat as, thermostat es and one normally open contact of relay 35. When humidistat 3 is satisfied it is open, and when thermostat 39 is satisfied it is open. humidistat at and the thermostat at are satisfled the compressor motor will not operate because the starting switch 38 will not be energized or closed.

When the humidistat lid is satisfied and open, and the thermostat 35 is not satisfied and therefore closed, relay 35 will be in its normally open position making contact between conductors $53 and Qi. Thus a circuit will be established to energize compressor motor starting switch 38 from conductor 89, through conductors Ed and 9! and the motor and compressor will be put into operation to run until thermostat 39 is satisfied.

When humidistat 34 calls for a reduction in humidity in the storage room it will become closed, and when closed it will make contact between conductors 88 and ac to energize relay t and transformer 35. ihe energizing of relay 35 makes a contact between conductors 89 and 9! to energize motor starter 38, causing the compressor motor and refrigeration system to operate until humidistat 3d becomes satisfied and opened. The energizing of transformer 36 in turn, energizes damper motor 26 through conductors $8 When both the iii and M. When thus energized damper motor 2'9 operates to pull on its linkage 2 ll-Ato accomplish functions hereinafter described.

When a storage machine embodying this .invention is put to use for controlling the relative humidity and temperature within a closed room, vault or storage space, it is usually installed against one wall as shown in Fig. 10. The three conductors of a three phase electrical power line are connected to the machine conductors ill, and i2 and pipe 55 is connected to a source of cooling water for the refrigeration condensing unit in the machine, pipe 5 3 is connected to :a drain to dispose of cooling water warmed by the machine and pipe to is connected to a drain to dispose of condensed water vapor. Two air :ducts 2 are assembled to the top of the machine at openings is to extend to the ceiling level of the room in which the machine is installed.

When the above listed connections are made, the following adjustments of the control instruments may be made for a fur storage vault, for example. The humidistat as is set for 55% relative humidity, the thermostat 351 is set for 60 degrees, the pressure switch 33 is set for an emergency high pressure cut-out at 1'75 pounds and a low pressure cut-out at 15 pounds; the defrosting timer 32 is set for stopping the condensing unit for 15 minutes out of each three hours of its running time. After the adjustments have been made the storage machine is put into operation by closing the manual switch 3| to its left hand position.

If the relative humidity in the storage room is less than 55% and the temperature less than 60 degrees, the switch contacts in both humidistat 3t and the thermostat 39 will remain open and the machine will not be called on to function. If the temperature in the room rises to 61 degrees, the thermostat 39 will close its contact to energize magnetic starter 38 which will cause the blower motor 8 and the compressor motor I6 to operate the refrigeration of the machine. Operation will then continue until the thermostat is satisfied by a temperature reduction to 60 degrees or less for which the thermostat is set. After each three hours of integrated compressor running time the defrosting timer stops the compressor while air circulation is maintained through the cooling coils to melt ofi any frost that may have accumulated thereon.

The blower 7 draws air from the ceiling level of the room through duct 27, down into cabinet i, through evaporators 5 where it is cooled; and discharges the cooled air through cool air duct iii into plenum chamber 5 i from whence it is discharged horizontally parallel to the floor at the floor level. When the room is cooled to less than 60 degrees for which the thermostat 39 has been set, then the thermostat contact opens and both the cool air blower and the condensing unit is caused to stop.

If the relative humidity in the room rises above 55%, regardless of the temperature or the position of the thermostat, then the humidistat contact will close to energize relay 35 which in turn will cause the damper motor 2t, the blower 1 and the condensing unit to operate. This condition of machine operation wil cause maximum reduction of relative humidity of air passing through the machine.

When damper motor is is caused to operate by the humidistat calling for a reduction in humidity, it pulls upward against spring as to close shutter 2i and open gates 2-3 and 25 in cool air duct It. When shutter 2| is closed the right hand air inlet to blower is closed. This reduces the C. F. M. capacity of blower 7 to approximately one-half by admitting air only to onehalf of the blower wheel through the left side opening in the blower housing. The reduced volume and velocity of air through evaporators 5 causes the evaporators to drop to a lower temperature which will cause increased condensation of water vapor from the air, The slower velocity of the air through the evaporators 5 will give added time for the air to give up its water vapor to the coil surfaces.

In the event the evaporator surfaces drop in temperature below the freezing point during a dehumidifying phase of operation, then the water vapor in the air will be collected on the evaporator surfaces in the form of frost or ice and the defrosting timer 32 will cause the frozen moisture to melt off in the fifteen minutes the condensing unit shuts off in each three hour period of operation by drawing air that is warmer than freezing through the coils 5.

When the cooled and dehumidified air is discharged by the blower down the cool air duct Iii, it is substantially in a saturated condition. Since gates 23 and 25 have been opened by the damper motor as during the dehumidifying phase of operation, part of the cooled air leaves cool air duct it through gate 23 and flows into the lower chamber l, which encloses the condensing unit, here this air becomes heated by the heat of operation of the compressor motor [6 and the compressor [5 and then it flows back into cool air duct It through open gate 2.5. The heating of this air reduces its relative humidity. This is a very important and useful result of this invention. Without the application of reheat to the cooled air flowing through a humidity controlling machine, the air discharged from the machine must be in substantially a saturated condition since moisture would not be rejected from the air at the cooling coils unless the air was cooled below its dew-point where it of necessity becomes saturated.

The storage of furs and all other dry merchandise that is adversely afiected by excess relative humidity, requires that its ambient air be of a relative humidity much less than saturation. When a refrigeration machine is used for extracting moisture from the air a means of reheating the air is necessary for the accomplishment of eihcient humidity control.

A machine embodying this invention is con structed to withdraw air from the ceiling level, to cool it, and then to discharge the cooled air horizontally at the floor level (see Fig. 10) The recirculation and cooling of air in an enclosed room in this way causes the air to move in the direction of naturally induced thermosyphonic connection. When the air in a room is cooled below outside temperature, then there is heat leakage into the room through the walls. The room air in contact with the walls becomes warmed. The warmed air rises to the ceiling level or the room because it is lighter in weight than the cooler air in the room. This natural thermosyphonic circulation of air in a room is encouraged and assisted by the use of machine constructed in accordance with this invention which specifies that the warmed air which collects naturally at the ceiling level shall be withdrawn from theceiling level by a duct 21 of themachine, cooled and dehumidifled within the machine and then discharged horizontally at the floor level.

In a test machine constructed in accordance with the specifications of this invention, a 5 H. P. condensing unit was used and a cool air blower having approximately 2,000 C. F. M. capacity discharged the cooled and dehumidified air at the floor level of a garment storage vault approximately 50 feet long by 25 feet wide and 12 feet high, having 15,000 cubic feet volume. The machine was placed at one end of the vault with the cool air discharge directed toward the opposite end wall, 50 feet distant. Fur and cloth garments were hanging in the vault suspended from racks that supported the garments to clear the floor by 14 inches to 18 inches, substantially as shown in Fig. 10 herein. In the open space under the garments the cooled air flowed along the floor of the vault and spreading out to cover substantially the whole floor area with a flow of cooled air, a distinct air how could be felt at the opposite end of the vault from the machine, almost 50 feet dist-ant. Identification tags tied to the garments with strings in the usual way were seen to move in the air fiow at this distance from the machine.

In this installation set up for testing, the total volume of air in the vault was recirculated through the machine, cooled, and recirculated through the vault approximately every eight minutes of machine operation. Throughout the vault uniform air temperatures were maintained consistently with an average floor to ceiling temperature difference averaging approximately three degrees. The relative humrity in the vault was maintained between 50% and 55% and the temperature in the vault was maintained between 58 degrees and 62 degrees during summer weather between 89 degrees and so degrees.

It is desirable to iumigate storage vaults in which garments, seeds and other products subject to insect infestation are stored. When a vault equipped with a machine embodying this invention is in need of fumigation, it may be readily accomplished by the use of a commercial liquid fumigant such as a 50-56 combination of carbon tetrachloride and ethylene dichloride, used in the following manner:

Manual switch 3! on the control panel of the machine is set in its central or on position to stopthe functioning of the machine for a period of approximately twenty-four hours to permit the warm-up to approximately the outdoors temperature. Warming the vault for the purpose of rendering more active the insects in the vault. Active insects breathe more rapidly and are, therefore, more readily subject to the toxic effects of fumigant fumes.

When it is desired to start the fumigation process, a quantity of liquid fun igant equal to one and one-half gallons for each 1,000 cubic feet of vault volume is put into the fumigant pan 5? at the base of the machine through the conduit 58 which opens to the outside of the A funnel may be used to assist in pouring the fumigant into this conduit. In some installations a conduit is connected to conduit and extended outside the vault to a pump which is arranged to pump the correct amount of fumigant into pan 5". When the correct amount or" liquid fumigant has been deposited in pan 5i, then the manual switch on the control panel of the machine is set in its right hand position t cause the blower only of the machine to operate. The blower I causes air taken from the ceiling 9 level of the vault to be discharged downward through duct i0, directly upon the surface of the fumigant liquid in pan The agitating action and spread of this air flow rapidly evaporates the liquid fumic'ant into the turbulent air stream which then flows through louvers i l in grille I 3 out of the machine over the floor area of the vault. The fumigant fumes mixed with air are recirculated throughout the vault from floor to ceiling induced by the suction of the air intake into ducts 27 and the forcible discharge through grille I 3 at the floor level. This fumigation process is usually continued for forty-eight hours and then stopped by the expelling of the fumigant fumes by a separate ventilating system.

It is to be understood that this invention is not to be restricted to the exact types of parts and the particular arrangement shown in the drawings since these may be modified under the teachings of this specification and will then come Within the scope of the appended claims without departing from the spirit and scope of this invention.

Having thus described vention, I claim:

1. In a unitary machine for circulating air and controlling humidity within an enclosure, a housing for said machine, a condensing unit and an evaporator in said housing, an. air inlet and an and explained my inair outlet for said housing, a humidistat external of said housing, a double inlet blower in said housing a double inlet partitioned blower wheel in said blower arranged to draw air through said air inlet opening and to move it through one side of said double inlet blower and said air outlet .1

opening, and means responsive to said humidistat for reducing the volume of air moved through said evaporator.

2. In a unitary machine for circulating air and controlling its humidity within an enclosure, 21.

housing for said machine, a horizontal partition dividing said housing into an upper chamber and a lower chamber, an evaporator and an air inlet opening in said upper chamber, a condensing unit and an air outlet opening in said lower chamber, a double inlet blower arranged to move air from said upper chamber to said lower chamher, a humidistat external of said housing, and means responsive to said humidistat for closing one air inlet opening in said double inlet blower.

3. In a unitary machine for circulating air and controlling its humidity within an enclosure, a housing for said machine, a horizontal partition dividing said housing into an upper chamber and a lower chamber, an evaporator, an air inlet opening and a blower in said upper chamber said air inlet opening being in the top portion of said upper chamber, a condensing unit and a duct in said lower chamber, a plenum chamber in the bottom portion of said housing under said lower chamber, an air outlet opening in said plenum chamber, said duct providing communication between said blower and said plenum chamber, a humidistat external of said housing, and means responsive to said humidistat for establishing an air circuit between said duct and said lower chamber.

4. In a unitary machine for circulating air and controlling its humidity and temperature within an enclosure, 9, housing enclosing said machine, a refrigeration condensing unit in said housing,

a refrigerant evaporator in said housing, a humidistat and a thermostat mounted external of said housing, an air inlet opening and an air outlet opening in said housing, a double inlet blower within said housing arranged to draw air through said air inlet opening and to move it through said evaporator and said air outlet opening, means responsive to said thermostat for operating said condensing unit, and means responsive to said humidistat, superseding said thermostat for operating said condensing unit and coincidentally closing one inlet of said blower.

5. In a unitary machine for circulating air and controlling its humidity within an enclosure, a housing for said machine, a condensing unit and an evaporator in said housing, an air inlet and air outlet for said housing, a humidistat external of said housing, a double inlet blower in said housing arranged to draw air through said air inlet opening and to move it through said evaporator and said air outlet opening, a double inlet centrally partitioned blower wheel in said blower, and means responsive to said humidistat for closing one air inlet of said double inlet blower.

6. In a unitary machine for circulating air and controlling its humidity within an enclosure, a housing for said machine, a humidistat external of said housing, a condensing unit and an evaporator in said housing, an air inlet opening in the upper portion of said housing, a duct communicating with said air inlet opening and the upper portion of an enclosure in which said machine is installed, an air outlet opening in the bottom portion of said housing positioned adjacent to the floor of said enclosure, a blower in said housing arranged to draw air through said air inlet opening and duct and to discharge it from said outlet opening, and means responsive to said humidistat for reducing the volume of air moved through said evaporator.

7. In a unitary machine for circulating air and controlling its humidity within an enclosure and. for periodically fumigating the enclosure, a housing for said machine, a humidistat external of said housing, a condensing unit and an evaporator in said housing, an air inlet openin in the upper part of said housing, a horizontal shallow pan for fumigant at the bottom portion of said housing, means for introducing fumigant into said pan, an air outlet opening in said housing adjacent to the top of said fumigant pan, a blower in said housing arranged to draw air through said air inlet opening and discharge it downward toward said fumigant pan, and means responsive to said humidistat for reducing the volume of air moved by said blower.

ALLEN TRASK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,837,798 Shipley Dec. 22, 1931 1,945,379 Roesch Jan. 30, 1934 2,236,058 Henney Mar. 25, 1941 2,286,491 Kucher June 16, 1942 2,369,511 Winkler Feb. 13, 1945 2,438,120 Freygang Mar. 23, 1945 2,497,068 Canney Feb. 14, 1950 2,528,720 Binder Nov. 7, 1950 

